Blasting cap



atented ar. 2U, 1934 BLASTING CAP Willardde C. Crater, Succasunna, N.3., assignor to Hercules Powder Company, Wilmington, DeL, a corporationof Delaware N0 Drawing. Application April 29, 1933, Serial No. 668,661

8 Claims. (Cl. 52-4) This invention relates to an improvement inblasting caps, and has for its object production of a blasting cap whichmay be readily and cheaply loaded and positively detonated, and whichwill be of high eificiency in detonating a blasting charge, as evidencedby the fact that the caps embodying this invention give excellent platetests; i. e. a large hole in the plate and a good sunburst.

This invention may be applied to either electric blasting caps, or toordinary blasting caps fired with a fuse.

Heretofore, electric blasting caps have been provided with a compressedcharge of mercury fulminate and a loose charge of mercury fulminate inwhich is embedded the bridgewire, or have been of the so-called basecharge type; i. e. have been provided with a base charge, not adapted tobe fired by the heat of the bridgewire, comprising, for example, picricacid, trinitrotoluene, tetryl, nitrostarch, ground smokeless powder,etc., and a top charge or priming charge detonated directly from theheat of the bridgewire embedded therein, and which when detonatedcommunicates detonation to the base charge. Such top charge maycomprise, for example, mercury fulminate, lead azide, leadtrinitro-resorcinate, etc.

The materials used heretofore for the base charge have not provedentirely satisfactory for one reason or another, as for example, becausethey are difficult to prepare in a form which will fiow readily, whichis a very important factor in cap loading, or because they are dusty,or, as in the case of picric acid, they have a tendency to attack themetal of the cap shell in the presence of small amounts of moisture, orbecause they are of unsatisfactory chemical stability.

In accordance with this invention, it has been found that a highlysatisfactory and eflicient lasting cap, of either the electric or fusetype, can be produced by the use of i-inositol nitrate, preferablyhexanitrate, as the explosive charge.

In the case of the electric blasting cap a charge of inositolhexanitrate alone may be used, or as a base charge underneath a suitabletop charge. In the case of a common cap to be fired with a fuse inositolhexanitrate as a base charge beneath a top charge comprising the usualinitiating or detonating agents, such as mercury fulminate, lead azide,lead trinitroresorcinate, etc. will be used, or alternatively, a topcharge comprising a mixture which burns without detonating, and evolveson burning a considerable amount of heat may be used, since I have foundthat a charge of inositol hexanitrate can be caused to detonateefficiently by heat alone, in contrast to the commonly used basecharges, which do not detonate by heat alone, but which requiresuperposition of, or admixture with, an initial detonating composition.

In the case of an electric blasting cap where inositol hexanitrate isused as a base charge the top charge may comprise the usual initiatingor detonating agents, such as mercury fulminate, lead azide, leadtrinitroresorcinate, etc. Where inositol hexanitrate is used alone thehot flash from the match head, in which is embedded the bridgewire (seeInitialexplosivstoffe, Escales und Stettbacher, 1917, page 467, whichdescribes match heads) will be sufiicient to cause detonation of thecharge of inositol hexanitrate without the interposition of a top orinitiating charge. By theterm match head, I include other shapes andforms, e. g., a straight bridgewire enclosed by non-detonating flashcompositions.

As illustrative of a satisfactory blasting cap in accordance with thisinvention, for example, any usual or desired form of blasting cap casingmay be charged with a base charge comprising 0.16 g. of inositolhexanitrate, the base charge being pressed under a pressure of about7840 pounds per square inch, over which, for example, is placed apriming charge of 0.30 g. of a 90/10 mercury fulminate-potassiumchlorate mixture, and over which, in turn, is placed a capsule and anigniting wafer comprising 0.10 g. of a /30 fulminatechlorate mixture,pressed at 5600 pounds per square inch. These caps will be sealed andprovided for firing by a fuse or electrically, in accordance with usualpractice.

As illustrative of a satisfactory electric cap in accordance with thisinvention, any usual form of blasting cap casing may be charged with asingle charge comprising .50 g. of inositol hexanitrate, pressed under apressure of about 7840 pounds per square inch. -In the plug seal of thecap is placed the usual match head igniter, or equivalent thereof, andthe whole sealed with pitch. On passing a heating current through thebridgewire embedded in the -match head, the match head is ignited, andgives a violent flash, which flash, I have found, is sulficient to bringto detonation the charge of inositol hexanitrate located in the vicinitythereof.

As illustrative of a satisfactory common or fuse type blasting cap inaccordance with this invention, any usual form of blasting cap may becharged with a base charge comprising .50 g. of inositol hexanitra-te,the base charge being pressed under a pressure of about 7840 pounds persquare inch, over which is placed an igniting (but not detonating)charge of 0.30 g. of a match composition comprising barium nitrate,magnesium powder and lead hypophosphite, overwhich is pressed aperforated capsule. When a fuse is placed in the open end of the cap,ignited, and the spark flashed through the opening in the capsule, the

compressed match composition will flash and burn without exploding andwill cause the charge of inositol hexanitrate thereunder to detonate.

If desired, in the case of use of inositol hexanitrate with priming(detonating) top charges, the inositol hexanitrate and detonating chargemay be mixed intimately. Thus, for example, inositol hexanitrate may bemixed with mercury fulminate or diazo-dinitrophenol, or the like, andthen pressed into the cap shell.

The caps made in accordance with this invention will be found to be ofsuperior strength and of special advantage in detonating dynamites. Inassociation with a priming charge of negative oxygen balance, inositolhexanitrate is of particular advantage because it possesses a positiveoxygen balance, thus eliminating the necessity, as, for example, withmercury fulminate, for the use of an oxidizing agent, as, for example,potassium chlorate, or the like.

It will now be understood that this invention contemplates, from thebroad standpoint, a blasting cap having a base charge, or a singlecharge of inositol hexanitrate. And it will be understood that the capotherwise may be of any type or form desired. It will be understood thatmore specifically the cap may include any primary initiating ornon-detonating flash charge, or a detonating charge for initiating ordetonating the inositol hexanitrate, and any other ingredients which maybe desired. It will be further understood that ii a detonating primarycharge be used it may in whole or in part be mixed with the inositolhexanitrate or superimposed thereon, all without departing from thisinvention, and it will be understood further that I do not limit myselfto any specified amount of inositol hexanitrate, initiating charge orother ingredients, or to the use of any particular pressure for pressingthe charge so long as excessive pressures which will cause dead pressingor bulging of the cap shell are avoided.

This application is a continuation in part of application filed by me,Serial No. 565,705, filed September 23, 1931.

What I claim and desire to protect by Letters Patent is:

l. A blasting cap for initiating commercial explosives including acasing and a charge of i-inositol nitrate in said casing.

2. A blasting cap for initiating commercial explosives including acasing and a charge of inositol hexanitrate in said casing.

3. A blasting cap for initiating commercial explosives including acasing and a charge of i-inositol nitrate and an initiator for theinositol nitrate in said casing.

'4. A blasting cap for initiating commercial explosives including acasing and a charge of inositol hexanitrate and an initiator for theinositol nitrate in said casing.

5. A blasting cap for initiating commercial explosives including acasing and a charge of i-inositol nitrate and a detonating initiator forthe inositol nitrate in said casing.

6. A blasting cap for initiating commercial ex- 105 plosives'including acasing and a charge of i-inositol nitrate and a flash initiator for theinositol nitrate in said casing.

'7. A blasting cap including a casing, a charge of i-inositol nitrateand a priming charge there- 110 in, the priming charge beingsuperimposed on the inositol nitrate.

8. A blasting cap including a casing, a charge of inositol nitrate and apriming charge therein, the i-inositol nitrate and priming charge being115 intimately admixed.

WILLARD DE C. CRATER.

